1. Field of the Invention
The present invention relates to a semiconductor cleaning method. More particularly, the present invention relates to a method of cleaning a dual damascene structure.
2. Description of the Related Art
A multiple interconnection process employs dual damascene structures. Thus, the reliability of the devices is increased. In addition, the process window is also increased. As the integration of the integrated circuit increases, dual damascene technology has become a main technology in the semiconductor industry.
In a Very Large Scale Integrated (VLSI) semiconductor process, a cleaning step performed in each fabrication stage is an important factor for obtaining high-quality devices. The wafer pollution includes particulates and film contaminates. Any particle that appears on the chip surface is called a particulate, which can come from the operation workers or the operation machines, such as the quartz pipes of a high-temperature furnace, a polished film or photoresist particles, and even the particles or bacteria from the deionized wafer. In addition, the film contamination is caused by a layer of contaminates that come from the outside deposited on the wafer. The layer of contaminates that come from outside include solvent residues, the residues of the developing solvent, etc.
FIG. 1A is a schematic, cross-sectional view showing a substrate after forming and cleaning a dual damascene opening in a conventional dual damascene process.
In FIG. 1A, a substrate 100 has a copper layer 102 therein. A dielectric layer 104 is formed over the substrate 100. A dual damascene opening 120 is formed in the dielectric layer 104. Usually, after the dual damascene opening 120 is formed, a cleaning step is performed with a dilute hydrogen fluoride (HF) solution. However, polymer residues 108 cannot be completely removed after the cleaning step is performed. In addition, the HF cleaning solution overly corrodes the copper layer 102, and thus resulting in a recess surface in the copper layer 102.
FIG. 1B is a schematic, cross-sectional view showing a substrate after performing a chemical mechanical polishing and a cleaning step in the conventional dual damascene process.
In FIG. 1B, a copper layer (not shown) is formed over the substrate 100 to fill the dual damascene opening 120. A chemical mechanical polishing (CMP) step is performed to remove the copper layer on the outside of the dual damascene opening 120. A dual damascene structure 122 thus is formed. Thereafter, a cleaning step is performed using an amine-containing solution, such as an ESC780 solution. However, as shown in FIG. 1B, hydrocarbon particulates 109, which are generated from the reaction between the dielectric layer 104 and the CMP slurry, and slurry residues 110 still remain on the surface of the dual damascene structure 122 after the cleaning step is performed.
Therefore, the disadvantage of the conventional method is that the polymer residues cannot be completely removed by the HF solution. In addition, the cleaning step performed after the CMP step cannot remove the hydrocarbon particles and the slurry residues. This, in turn, causes a rough surface forming in a wafer. Consequently, a subsequent photolithography process fails.
The invention provides a method of cleaning a dual damascene structure. A first conductive layer is formed in a substrate. A dielectric layer is formed over the substrate. A dual damascene opening is formed in the dielectric layer to expose the first conductive layer. A H2O2 based aqueous solution is used to remove polymer residues in the dual damascene opening. A temperature of the H2O2 based aqueous solution is controlled so that the first conductive layer is not corroded. A diluted HF solution or a diluted HF and HCl solution is used to remove the polymer residues. A second conductive layer is formed over the substrate to fill the dual damascene opening. A chemical mechanical polishing process is performed with the dielectric layer serving as a polishing stop to remove the second conductive layer outside the dual damascene opening. A H2O2 based aqueous solution is used to clean the hydrocarbon particulates from the chemical mechanically polishing step. A diluted HF solution or a diluted HF and HCl solution is used to remove the slurry residues, such as silicon oxide of the slurry, from the chemical mechanical polishing step.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.